Here is an alternate way of repairing an end can if the carbon-kevlar tube is not totally junked and replacing is not mandatory.

The part of the damaged tube must be removed. I would still be comfortable if the rest of it is 20cm in length at least. Use a piece of thick sandpaper to mark your cutting line. Any metal saw will do the rest of the job.

The same length should be removed from the perforated pipe.

And then welded back in again if necessary.

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Piston to barrel clearance

something everyone should have in his toolbox. Piston fit fillers are cheap and very useful. You will need 0.002, 0.0025 & 0.003 inch feeler guages as these will cover most of your needs.

you can pay up to £400 for a set of feeler gauges not what id pay but you can if you want